The flat mattress with planar top surface has been used for at least two thousand years. It has been taken granted that a mattress has a planar flat top surface. But this is not unchallengeable.
It is noted that many infants younger than three months are very sensitive to the outside worlds. Their hands are moving and grasping in the air. They can be easily startled even by a mini-tiny sound or air movement. When they are placed in a belly-sleeping position, however, their palms and fingers touch the mattress and they fell asleep quickly.
Belly-sleeping must be under close supervision because sudden infant death syndrome (herein after as SIDS) occurs in belly-sleeping position is more often than that in sleeping-on-the back position. Infants are more likely to have apnea (pauses in breathing) when they sleep on their stomachs on flat beds. They are also more likely to re-breathe the air they have just exhaled, which can raise their levels of carbon dioxide. The increased retention of body heat can also be dangerous for some infants. It is estimated that belly-sleep in conventional flat bed has up to many times the risk of death as back-sleep. In response to the statistics, the medical professionals simply advocate against belly-sleep and promote back-sleep.
What is desired is an apparatus which enables belly-sleeping and decreases the possibility of SIDS by reducing the weight of the baby's head applied on her face and nasal area and increasing the baby's ability to turn her head.